Help > Authoring > Using Markup > Working with Invalid Markup > Changing an Attribute Value for Invalid Markup
  
Changing an Attribute Value for Invalid Markup
Choose Edit > Modify Attributes dialog box. The dialog box shows valid and invalid attributes and values that exist for the tag. Declared attributes with invalid values will be displayed in red. Any undeclared attributes will be displayed in red strikethrough.
This is an image of the Modify Attributes dialog box showing an invalid attribute.
You can delete any attribute (declared or undeclared) by using the Delete or Delete All button or by highlighting and deleting the attribute value.